<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{
            
            border: 1px solid rgb(140, 140, 200);
        }
        .box{
            display: flex;
            flex-direction: column;
            height: 100vh;
           
        }
        .box .header{
            flex: 1;
            height: 20vh;
            background-color: gray;
        }
        .center{
            flex: 5; 
            display: flex;  
            border: none;  
        }
        .left {
            flex: 3;
            display: flex;
            flex-direction: column;
            
        }
        .left .up{
            flex: 2;
            border-bottom: 1px solid rgb(140, 140, 200);
        }
        .left .down{
            flex: 2;
            border: none;
        }
        .right{
            flex: 1;
            display: flex;
            flex-direction: column;
            border: none;
        }
        .right .up{
            flex: 1;
            border-bottom: 1px solid rgb(140, 140, 200);
        }
        .right .center{
            flex: 4;
            display: flex;
            flex-direction: column;
            border-bottom: 1px solid rgb(140, 140, 200);
        }
        .right .down{
            flex: 5;
            border: none;
        }
        textarea{
            width: 85%;
            height:80%;
            margin: 10px; 
            border:none; 
            padding: 10px;
            resize: none;
        }

        input{
            width: 55px;
            height: 35px;
            color: white;
            background-color: rgb(73, 160, 231);
            border-radius: 15%;
            position:absolute;
            right: 330px;
            bottom: 3px;
            cursor: pointer;
        }
        p{
            border: none;
        }
        .lb{
            color: rgb(46, 128, 190);
            border: none;
            font-size: 20px;  
            margin-left: 20px;
        }
        .gb{
            color: rgb(46, 128, 190);
            border: none;
            font-size: 20px;
            margin-left: 20px;
        }

    </style>
</head>
<body>
    <div class="box">
        <div class="header"><span>用户：张三</span></div>

        <div class="center">

            <div class="left">
                <div class="up">
                    <p>张三：你好</p>
                </div>
                <div class="down">
                    <textarea name="" id="" placeholder="在此输入文字信息..." ></textarea>
                    <input type="button" value="发送">
                </div>

            </div>

            <div class="right">
                <div class="up"><span class="lb">好友列表</span></div>
                <div class="center">
                    <p>张三</p>
                    <p>李四</p>
                </div>
                <div class="down"><span class="gb">系统广播</span></div>

            </div>

        </div>

    </div>
    
</body>
</html>